It huffed and puffed, and helped researchers

Friday

Oct 13, 2006 at 12:10 AM

BY JENNIFER KAYTHE ASSOCIATED PRESS

SWEETWATER - The man-made tropical storm slammed into the faded, one-story concrete house. The front door banged open, the tarpaper roof peeled back, the living room curtains shredded and the masking tape crisscrossed on the windows flapped apart in mere minutes.
The 115-mph blasts of air and rain Thursday came from the "Wall of Wind," two 500-horsepower fans stacked 16 feet high to simulate conditions in a Category 3 hurricane.
Parked about five feet from the front door of a house slated for demolition, the device gave researchers from Florida International University's International Hurricane Research Center the first look at how a real building deteriorates under severe wind and rain.
Most other storm simulations have been conducted in wind tunnels with small-scale construction models, said Stephen Leatherman, the research center's director.
"You can't scale down gravity. You can't scale down a house to the size of a birdhouse and learn anything from a shingle the size of an ant," Leatherman said.
Thursday's test gradually built from tropical storm strength.
The walls of the reinforced concrete block house, built in the 1940s, withstood the 115-mph winds for 10 minutes without damage. So did the glass window panes, until an FIU graduate student tossed clay tiles and small chunks of wood into the air in front of the fans to simulate wind-borne debris.
"With appropriate hurricane impact shutters and a better roof it would have made it through a Category 4," Leatherman said.
But about 2 inches of water sprayed from nozzles on the wind machine saturated the inside of the disheveled house, showing the potential for water and mold damage in this low-lying Miami suburb flooded in 1999 by Hurricane Irene.
Lab tests with the fan wall on layers of terra cotta roof tiles and mock buildings constructed by researchers have uncovered some common structural flaws, such as air vents that trap water inside buildings, which causes ceilings to collapse, and weakening where a roof connects to a wall.
Those tests have led researchers to develop new technologies to make the roof-wall junctions more aerodynamic and secure in a storm, said Arindam Gan Chowdhury, an FIU professor of wind engineering.
"When we have hurricanes, you have a lot of suction force on a roof. That's the main reason for the roof to lift off," Chowdhury said.
Researchers said the fan wall, which can generate winds up to 123 mph, is a prototype for a six-fan unit under construction that will generate winds up to 130 mph.
A lab big enough to contain a 2,500-square-foot house and an 18-fan unit capable of producing Category 5 hurricane winds up to 160 mph is also planned.
Forecasters consider storms of Category 3 strength and stronger to be major hurricanes.
The FIU researchers filmed parts of a public service announcement on hurricane preparedness before the demonstration. The masking tape copied a misguided attempt some residents make to keep their windows from shattering.
"We're going to show that's not adequate," Leatherman said.